CH3CH2SH

CH3CH2SH, commonly known as ethanethiol or ethyl mercaptan, is an organosulfur compound containing a thiol (-SH) group attached to an ethyl moiety. Its molecular formula is C2H6S, and its structure is CH3-CH2-SH. It is classified as an alkanethiol.

Ethanethiol is a colorless to pale yellow liquid at room temperature and is highly volatile. It has a very strong, unpleasant odor often described as similar to rotten onions or garlic. The substance is flammable, and its vapors can form explosive mixtures with air. Because the odor threshold is extremely low, small exposures are perceptible, though olfactory fatigue can occur with prolonged exposure.

Industrially, ethanethiol is produced by thiolation of ethyl halides, using reagents such as sodium hydrosulfide. It can also be prepared via the thiourea method, where ethyl halide reacts to form an isothiouronium salt that is hydrolyzed to the thiol. Purification is typically achieved by distillation due to its volatility.

As a thiol, ethanethiol participates in common sulfur–containing compound chemistries, including oxidation to form disulfides and deprotonation to generate thiolate anions. It serves as an intermediate in organic synthesis and is widely used as an odorant for natural gas to provide detectable leakage alarms, a practical application that relies on its characteristic smell.

Safety considerations for ethanethiol include its flammability and potential toxicity. It can irritate the skin, eyes, and respiratory tract. Proper handling requires adequate ventilation, avoidance of ignition sources, and appropriate personal protective equipment.